1. Technical Field
This invention relates to an endovascular prosthesis for implantation within and treatment of a human or animal body for the repair of damaged vessels, ducts, or other physiological passageways. In particular, this invention relates to a device for the treatment of aortic arch disease and more particularly to the treatment of a form of aortic aneurysm known as an aortic dissection in the ascending thoracic aorta.
2. Background Information
The functional vessels of human and animal bodies, such as blood vessels and ducts, occasionally weaken or even rupture. In some case a dissection forms in the aorta. An aortic dissection is a form of aneurysm to the descending aorta in which the wall of the aorta is damaged to such an extent that blood under pressure can get between inner and outer layers of the wall of the aorta to expand part of the wall into an inflated sac of blood which is referred to as a false lumen. The inflated sac of blood or false lumen so formed may extend some distance down the descending aorta and open out into the aorta again further down. The result is an acute aortic dissection, which is also known as an aortic dissection or acute aortic syndrome. Those who suffer from this condition usually have an abnormally weak aortic wall before the dissection occurs. Subjects with thoracic aortic aneurysms are at risk for aortic dissections. In Western European and Australian men who are between 60 and 75 years of age,  aortic aneurysms greater than 29 mm in diameter are found in 6.9% of the population, and those greater than 40 mm are present in 1.8% of the population.
Aortic dissections are classified by either the DeBakey System or the Stanford system. A dissection involving both the ascending and descending thoracic aorta is classified as a type I dissection under the DeBakey System. A type II dissection involves a dissection of just the ascending thoracic aorta. Under the Stanford system, type I and II DeBakey dissections are considered type A dissections. A dissection confined to just the descending aorta is considered a type III DeBakey dissection or a Type B Stanford dissection.
If a dissection of the descending thoracic aorta occurs, some patients can be treated with medicaments to handle their blood pressure such that surgery may not be necessary. However, if a dissection of the ascending thoracic aorta occurs, immediate surgery is needed to replace it. One surgical intervention method involves the use of a prosthetic device to provide some or all of the functionality of the original, healthy vessel, and/or preserve any remaining vascular integrity by replacing a length of the existing vessel wall that spans the site of vessel failure.
Ideally, the failed portion of the vessel is sealed off and the weakened vessel walls are supported. For weakened or aneurysmal vessels, even a small leak in the prosthesis may lead to the pressurization of, or flow in, the treated vessel which aggravates the condition the prosthesis was intended to treat. A prosthesis of this type can, for example, treat dissections of the thoracic aorta by implantation at the site of the initial tear of the dissection to seal the tear and thereby stop the flow of blood into the false lumen created by the dissection.
A prosthetic device can be of a unitary construction or be comprised of multiple prosthetic modules. A modular prosthesis allows a surgeon to accommodate a wide variation in vessel morphology while reducing the necessary inventory of differently sized prostheses. For example, aortas vary in length, diameter, and angulation. Prosthetic modules that fit each of these variables can be assembled to form a prosthesis, obviating the need for a custom prosthesis or large inventories of prostheses that accommodate all possible combinations of these variables. A modular system may also accommodate  deployment options by allowing the proper placement of one module before the implantation of an adjoining module.
Proper implantation of prosthetic devices used to treat dissections rests on proper placement. Given the relatively small size of the ascending aorta, for instance, ideal anchoring positions for prosthetic devices are few. It is therefore the object of the present invention to provide a prosthetic device with a suitable fixation geometry for secure implantation in the ascending thoracic aorta.